*{
    margin:0;
    padding:0;
}
body{
    background:pink;
}
.box001{
    padding:20px;
    width: 100%;
    background-color:lemonchiffon;
}
#mouseEvents{
    background:yellow;
    width: 20%;
}

#mouseEvents:hover{
    background:green;
    width: 20%;
}